Migrate s390x AES-XTS to standard HW interface

Migrate s390x AES-XTS to standard HW interface

Move the s390x-specific AES-XTS implementation from `cipher_aes_xts_s390x.inc`
to `cipher_aes_xts_hw.c`, adapting it to use the standard `PROV_CIPHER_HW`
dispatch structure.

This refactoring removes standalone initialization wrappers and integrates the
s390x hardware backend more cleanly with the generic AES-XTS provider code. It
also reduces code duplication by relying on the generic layer for common
validations (such as the maximum blocks per data unit limit) before invoking
the hardware-specific stream cipher.

Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Norbert Pocs <norbertp@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
MergeDate: Sat Jun 27 09:05:46 2026
(Merged from https://github.com/openssl/openssl/pull/31472)